Many industrial processes generate combustible effluents as a byproduct of the process, and commonly such processes are those which require heat energy in order to be carried out, as for example, in paint enamel drying ovens in which the ambient air is heated to a high temperature to bake the paint which drives off the solvents which are typically of a combustible hydrocarbon base.
The discharge of such effluents directly into the atmosphere has been severely limited by governmental regulation in recent years, such that such effluents must be removed or otherwise eliminated from the air exhausted to the atmosphere.
It has heretofore been known to those skilled in the art that an effective method of eliminating such combustible vapors or effluents is to incinerate the same in a high temperature incinerator. For example, the air exhausted from the paint drying oven passes into an incinerator, which heats the air to a sufficiently high temperature to cause substantially complete combustion of the hydrocarbon vapors into relatively harmless carbon dioxide and water vapor. This process is also effective for removing relatively lightweight solids such as resin particles entrained in the exhaust air stream.
While effective, such processes have basically required substantial additional heat energy to be expended in the system, which raises the overall energy requirements of the particular process.
It has been known that the energy created by burning of the hydrocarbons or other effluents can be reduced by the preheating of the air to be incinerated through a heat exchanger, which heat exchanger also receives the products of combustion such as to transfer a portion of the heat energy of the incineration process into the incoming air to thereby reduce the energy requirements of the incinerator.
A further arrangement for improving the overall efficiency of the process is to pass the incoming fresh air supply through a heat exchanger for which the products of combustion of incinerated air are passed in order to preheat the fresh air supply to reduce the energy requirements for the process.
U.S. Pat. No. 3,917,444, issued to the present inventor, describes various such systems in this context and in which the waste heat generated is utilized in the primary process by recirculation of a portion of the products of combustion to the process, or is used to heat air circulated to the process by a heat exchanger. However, primary heat supplying burners are employed.
While such improvements in efficiency have enhanced the feasibility of this particular approach in eliminating combustible effluents, the overall efficiency is still relatively low and the energy requirements for the process have not substantially been reduced by the utilization of the incinerator heat energy, particularly for applications whereat the effluent level is relatively low.
Accordingly, it is an object of the present invention to provide an improved system and process for incinerating combustible effluents generated in a primary process such as in a paint drying oven, in which high efficiency utilization of the heat energy generated in the incinerator in the primary process is achieved.
It is a further object of the present invention to provide such efficiency system which employs a minimum number of components and which is reliable and trouble free in operation.